If I can use the crank on a hand-crank radio for about 30 seconds to get 15 minutes of emergency radio (not sure about those numbers) then it seems reasonable to me to assume that if I can haul up a 10kg mass 2 meters if would be enough energy to give me at least the same. The mass could even be the radio itself (with added water for extra mass) and the bottom of the rope would feature the ear plugs you use to listen.

wouldn't that be:98N x 0.002m/s = 0.196W?

Surprisingly enough that does not seem to be sufficient for a radio of 0.5W. Hmmm...I wonder if I could even use a geared cranking mechanism to get the 10kg up the 2 meters with applying the same force. Cranking those radios for 30 seconds just does not seems that hard. This appears wrong. Is my math (and thinking) right?

The crank radios with batteries stink since the batteries that are recharged by the generator sooner or later don't hold a charge any longer. I like the capacitor concept. They may outlast batteries in their ability to hold a charge.

The above calculations assume no frictional losses, in reality you’d be lucky to get 50% efficiency,e.g. the radio only runs for one pop song about 200 seconds long before you have to haul up the weight again.

[ 10Kg dropping freefall 2m could be a safety hazard, e.g. if the fixture your apparatus was suspended from gave way ]

Well, I just checked and one source says that cranking the crank for 1 minute gives you about 4 minutes of radio play. I guess that makes sense considering the numbers. They are certainly not as efficient as I thought.

And yes, a mass suspended about 2 meters high is about a dangerous as a high bookshelf or a potted plant on a balcony. People who find themselves needing to use an emergency radio may be willing to take this crazy risk though.

Well, I just checked and one source says that cranking the crank for 1 minute gives you about 4 minutes of radio play. I guess that makes sense considering the numbers. They are certainly not as efficient as I thought.

Is it a Chinese Radio?

I've tried some crank and shake flashlights and radios. The ads always seem to be a bit optimistic. I don't think I could hardly get the radio to play without constantly cranking (until the crank broke off). And, the cranking was always a bit noisy, so no sitting back and enjoying the radio.

A lot will depend on how much you need to amplify the sound. An unamplified walkman or ipod or similar really won't take much power.

Geezer's no power radio sounds like a good idea, as long as you don't mind using ear buds.

And yes, a mass suspended about 2 meters high is about a dangerous as a high bookshelf or a potted plant on a balcony. People who find themselves needing to use an emergency radio may be willing to take this crazy risk though.

Your 10Kg weight suspended from some improvised attachment close to the ceiling is certainly more hazardous than using AA batteries. 10Kg is heavier than a bowing ball, 2m is the height of a typical door.

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Think of this like dropping a bowling ball onto your foot - the weight of the ball compresses (squashes) the tissues of your foot against the floor. This force of this weight being dropped can rupture blood vessels, causing bruising, and even break bones. Dropping a bowling ball onto the stomach could compress the bowel, causing it to rupture, spilling the contents into the abdominal cavity and becoming a major source of infection.

The old crystal sets used a long length of wire suspended quite high to pick up a strong-enough signal to power earphones. This would be good for receiving emergency AM radio broadcasts (assuming the tornado/earthquake/flood didn't knock over your antenna too!).

By winding the inductor coil on a ferrite rod, you could pick up signals without an external antenna - this made it more portable. Also, it was directional, so you could work out where the transmitter was located.

Your 10Kg weight suspended from some improvised attachment close to the ceiling is certainly more hazardous than using AA batteries.

I agree.But the point was to find a reliable solution to power a radio in case batteries are not available and are desperately needed to hear learn what is going on with the help of a radio. Gravity can be found anywhere on this planet all the time and I was wondering if it could be used to power a radio. The discussion whether producing electricity this way is dangerous is besides the point since such an long-term emergency is inherently dangerous. Just having no shelter and water will kill many "civilized" people. Those who are smart and tough enough to have handled this will also be able to be careful about hanging something heavy in a tree.

I've seen hand crank radios that were supposed to store energy in batteries or capacitors. But, they never seemed to be very effective. And, of course solar radios.

I thought I had heard of a record lathe that was powered by weights, but I don't see any notes on the internet, and I can't remember which band it was in reference to.

Hand crank radios are in quite general use in remote parts in SouthEast Asia. Our son brought one back with him from the Philippines (he was working on a volunteer project in a village there). I think you would also find them in Indonesia and Papua Niugini. They seem to work quite well.

No, I am not talking about some miracle energy device, I am talking about pulling up a mass and letting it drop (slowly with the help of gears) to run a generator.

Has anyone here seen anything like this to operate, say, a small radio?

I have built the Radio Shack radio that uses no batteries. It works great, but I had to reverse the antenna and ground wire, to make it work. You can definitely pick up strong AM stations with it, and listen to them.

A small single traic AM radio with amplifier transformer, actually has the gate of the traic, initiated by the power from the antenna. I thought that was pretty cool.

i realize this post is real dead, but I came across it while researching, and have a relevant link. newbielink:http://www.indiegogo.com/projects/282006 [nonactive] if you haven't seen this, its a "potential energy" powered light that was crowdfunded recently called the GravityLight

DAB digital radios take a lot of power. An older, good quality analog-tuned FM radio (a Sony ICF-450L), driving headphones, only needs a few milliamps at 4volts, so little over 0.01 watt. A set of 3 AA batteries will last for many months of listening as a few hours per day. When batteries last that long, it's hardly worth looking for alternatives!But if you did want to solar- or otherwise power it - it makes sense to start with a minimal-power radio.

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